Systems and methods for inspecting a wafer with increased sensitivity

Abstract

Systems and methods for inspecting a wafer with increased sensitivity are provided. One system includes an inspection subsystem configured to direct light to a spot on the wafer and to generate output signals responsive to light scattered from the spot on the wafer. The system also includes a gas flow subsystem configured to replace a gas located proximate to the spot on the wafer with a medium that scatters less of the light than the gas thereby increasing the sensitivity of the system. In addition, the system includes a processor configured to detect defects on the wafer using the output signals.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention generally relates to systems and methods for inspecting a wafer with increased sensitivity. Certain embodiments relate to systems and methods for inspecting a specimen that include replacing a gas proximate to an illuminated spot on the wafer with a medium that scatters less light than the gas thereby increasing the sensitivity of the inspection. [0003] 2. Description of the Related Art [0004] The following description and examples are not admitted to be prior art by virtue of their inclusion in this section. [0005] Fabricating semiconductor devices such as logic and memory devices typically includes processing a specimen such as a semiconductor wafer using a number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. For example, lithography is a semiconductor fabrication process that typically involves transferring a pattern to a re...

AI Technical Summary

Benefits of technology

[0016] One embodiment relates to a system configured to inspect a wafer. The system includes an inspection subsystem configured to direct light to a spot on the wafer and to generate output signals responsive to light scattered from the spot on the wafer. The system also includes a gas flow subsystem configured to replace a gas located proximate to the spot on the wafer with a medium that scatters less of the light than the gas thereby increasing the sensitivity of the system. In addition, the system includes a processor configured to detect defects on the wafer using the output signals.

[0018] In another embodiment, the gas flow subsystem is configured to replace the gas with the medium only at a location proximate to the spot on the wafer. In an additional embodiment, the system includes a housing surrounding one or more optical components of the inspection subsystem. In one such embodiment, the gas flow subsystem is configured to purge the housing using the medium and to maintain a positive pressure in the housing using the medium such that photodecomposition of materials on the one or more optical elements is reduced.

[0021] Another embodiment relates to a gas flow subsystem configured to be coupled to an inspection system. The gas flow subsystem is configured to replace a gas located proximate to a spot on a wafer illuminated by the inspection system during inspection with a medium that scatters less of the light than the gas thereby increasing the sensitivity of the inspection system. The gas flow subsystem may be further configured as described herein.

[0022] An additional embodiment relates to a method for inspecting a wafer. The method includes inspecting the wafer by directing light to a spot on the wafer and generating output signals responsive to light scattered from the spot on the wafer. The method also includes replacing a gas located proximate to the spot on the wafer during inspecting with a medium that scatters less of the light than the gas thereby increasing the sensitivity of the inspecting. In addition, the method includes detecting defects on the wafer using the output signals.

[0024] In one embodiment, replacing the gas includes replacing the gas with the medium only at a location proximate to the spot on the wafer. In another embodiment, the method includes purging a housing surrounding one or more optical components used for inspecting with the medium and maintaining a positive pressure in the housing using the medium such that photodecomposition of materials on the one or more optical components is reduced.

Problems solved by technology

For instance, as the dimensions of semiconductor devices decrease, detection of defects of decreasing size has become necessary since even relatively small defects may cause unwanted aberrations in the semiconductor devices.

The best performance of most commercially available inspection systems does not meet these sensitivity and throughput performance requirements.

However, reducing the spot size also reduces the throughput of the system since scanning a smaller size spot over an entire wafer surface takes longer than scanning a larger size spot over the wafer surface.

Therefore, improvements in sensitivity expected based on improvements in the wafer surface quality cannot be achieved.

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